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<div class="chapter">
<div class="titlepage"><div><div><h2 class="title">
<a name="migration-1"></a>Migration from 1.X versions</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="sect1"><a href="migration-1.html#id-1.2.8.2">GdaValue and GdaDataModel changes</a></span></dt>
<dt><span class="sect1"><a href="ch07s02.html">GdaClient, GdaConnection and GdaError</a></span></dt>
<dt><span class="sect1"><a href="ch07s03.html">Various API changes</a></span></dt>
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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id-1.2.8.2"></a>GdaValue and GdaDataModel changes</h2></div></div></div>
<p>Libgda values were stored in <code class="classname">GdaValue</code> structures, this is no longer the case
      as the standard <code class="classname">GValue</code> container is now used. As a consequence data types are now
      identified by their <code class="classname">GType</code> identifier, there is thus no more any 
      <code class="classname">GdaType</code> definition.</p>
<p>The <code class="classname">GdaDataModel</code> has been transformed into an interface (as defined by the Glib 
      object system), and the old <code class="classname">GdaDataModel</code> has been replaced by the 
      <code class="classname">GdaDataModelRow</code> class. No code using the <code class="classname">GdaDataModel</code> should
      assume that data is internally stored as rows (vectors) of values as it was the case in the previous
      stable release.
    </p>
<p>In the new version, many objects implement the 
      <code class="classname">GdaDataModel</code> interface for various usages which did not exist in the previous version
      such as data import and filtering. <code class="classname">GdaDataModel</code> objects should now be considered
      as non writable, and if they need to be modified, the modifications permissions should be checked
      using the <code class="function">gda_data_model_get_attributes_at()</code> function. See the
      section about the various data models for more information. 
    </p>
<p> The following UML schema shows the various implementations of the <code class="classname">GdaDataModel</code> 
      interface and what they are for. Note that the
      <code class="classname">GdaDataModelRow</code> should not be instantiated directly but either
      used as a base class, or used through its children classes.
    </p>
<p>
      </p>
<div class="mediaobject"><img src="DataModels.png" alt="Various implementations of the GdaDataModel interface"></div>
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    </p>
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